Ester additives



United States Patent 2,993,773 ESTER ADDITIVES Verner' L. Stromberg, Webster Groves, Mo., assignor to Petrolite Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Filed Feb. 2, 1959, Ser. No. 790,353 6 Claims. (Cl. 52-415) This invention relates to deposit modifiers for substantially hydrocarbon fuels. More specifically, this invention relates to substantially hydrocarbon fuels containing deposit modifiers which inhibit and/r prevent the deposit-forming tendency of hydrocarbon fuels during combustion, and/ or modify the deleterious effect of the formed deposits, in both leaded and unleaded fuels, particularly in gasoline, jet fuels, etc., and to the process of inhibiting and/or preventing and/or modifying the formation deposits in engines employing hydrocarbon fuels.

The smooth operation of an internal combustion engine depends on the gradual propagation of the flame toward the cylinder walls and if the fuel-air mixture is ignited at many spots at the same time, progressive combustion is interrupted. If several compressive waves are created, they subject the unburned charge to unduly high pressure and temperature so as to produce engine knock. This generally occurs if the cylinder deposits, which contain carbonaceous materials and lead compounds, retain sufiicient heat to ignite the fuel-air mixture before the flame which had been originated by the spark plugs reaches all parts of the combustion chamber. Deposited lead compounds are believed to lower the temperature at which the deposits glow and ignite the fuel and it is desirable to reduce the deposits and/or neutralize the catalytic effect of such deposits in igniting the fuel. By so doing, these additives lower the octane number required to prevent knock or surface ignition.

As automobile manufacturers annually raise the compression ratio of their automobile engines in the race for higher horsepower, the need becomes greater for gasolines which burn cleanly, that is, have low depositforming tendencies. Engine deposits which find their origin in the fuel are primarily responsible for surface ignition phenomena such as preignition and octane requirement increase (ORI) which is the tendency of spark ignition engines in service to require higher octane fuels for proper performance. As a consequence, gasoline manufacturers have placed increasing stress on reducing the deposit-forming tendencies of their fuels and have resorted to various additives either to reduce the amount of deposits or to minimize their effects.

The deposits formed in the combustion zone, particularly on the piston head and the exhaust valves, appear to have the most immediate effects upon engine performance in that their presence requires a fuel having a higher octane rating in order not to knock, than is required by a new or clean engine. This means, in other words, that the octane value of a fuel required by an engine containing deposits in the combustion zone in order not to knock (refer-red to hereinafter as octane requirement) is higher than the octane requirement of a clean engine. For example, a clean engine which requires a gasoline having an octane rating of 60 in order not to knock is said to have an octane requirement of 60. If the same engine, when dirty, i.e., with deposits in the combustion chamber, requires a gasoline having an octane rating of 75 in order not to knock, such an engine is said to have an octane requirement of 75, or an octane requirement increase of 15. If a clean engine starts to get dirty, the octane requirement rises with continued use. Finally there is no more octane requirement increase with continued use and apparently ice the engine has then become as dirty as it is ever going to be with continued use, or if it becomes dirtier after a certain point, it does not require a gasoline of greater octane value in order not to knock.

It has been found, for example, that the weight of material deposited upon the top or head of the piston reaches a maximum in a single cylinder engine after approximately 20 hours of operation and that thereafter it decreases slightly, possibly due to a flaking action, until it levels off after about 40 hours of operation. It has also been found that the weight of the material deposited upon the exhaust valves reaches a maximum in the same engine after about 30 hours of operation and thereafter it decreases slightly and levels off after about 40 hours of operation. The fact that the weight of deposits in the combustion zone first reaches a maximum value and then levels off to a somewhat lower value while the octane requirement levels off at the maximum value is believed to disprove the formerly accepted theory that the octane requirement of an engine is proportional to the weight of deposits in the combustion chamber.

The undesirable effects of the deposits in the combustion chamber are further aggravated when tetraethyl lead is contained in the fuel because these deposits then are no longer primarily carbonaceous but contain appreciable quantities of lead. Accordingly, it has been found that the total weight of deposits formed in the combustion zone is appreciably greater when using a leaded fuel than when using a non-leaded fuel. The octane requirement increase of an engine operating on leaded fuel, however, is not in proportion to the difference in deposit weights. From this it is concluded that the octane requirement increase of an engine is determined not so much by the quantity of material deposited as by its presence and character.

It has also previously been found that the increase in octane requirement resulting from the formation of engine deposits is not attributable to a decrease in the thermal conductivity of the surfaces enclosing the combustion zone.

Since it has been found that the octane requirement increase of an engine is not determined solely by the quantity of material deposited in the combustion zone and that it is not due to a decrease in the thermal conductivity of the surfaces enclosing said zone, it is believed that it is due to a catalytic action wherein the deposits in the combustion zone act as catalysts to accelerate the oxidation of petroleum hydrocarbons. It has, therefore, been suggested that the proper approach to the problem of reducing the octane demand increase of an engine is that of adding to the fuel a substance having an anti-catalytic effect, or in other words, the effect of suppressing or inhibiting the catalytic properties of the depoits formed, especially the troublesome leadcontaining deposits.

The use of lead compounds in gasolines to increase the octane ratings thereof is extremely widespread. There are, however, several rather serious adverse effects which accompany the use of leaded gasolines. One of these effects, the deposition of various lead compounds within the combustion chambers of the engines, has been at least partially remedied by the use of halohydrocarbon scavengers such as ethylene dibromide and related compounds, for example, those disclosed in U.S. Patents 2,398,281, 2,490,- 606, 2,479,900, 2,479,902, 2,479,901, 2,479,903, etc. Another adverse eifect, which has been attributed to thelead anti-knock compounds is mis-firing due to spark plug fouling. This spark plug fouling is quite prevalent under conditions of high temperature engine operation and, particularly in the case of aircraft engines is a very serious type of trouble.

As stated above, there has been a marked trend in recent years in the automotive industry toward utilizing internal combustion engines having high compression ratios in passenger cars and trucks. It has been found that this increase in compression ratios results in increased engine efliciency whereby the motoring public is provided with both greater power availability and greater economy of operation. High compression engines almost uniformly operation. Of the several methods of raising the octane number of gasoline developed to date, that of utilizing an anti-knock agent, particularly of the organolead type, has been most successful. Although such anti-knock agents have been provided with corrective agents commonly known as scavengers, which effectively reduce the amount of metallic deposits in the engine by forming volatile metallic compounds which emanate from the engine in the exhaust gas stream the accumulation of engine deposits in combustion chambers and on other engine parts such as pistons, valves, and the like cannot be entirely prevented. This accumulation of deposits is particularly prevalent when the vehicles are operated under conditions of low speed and high load as encountered in metropolitan localities. As a result of the notable improvements in fuel anti-knock quality, which have been made in recent years, such deposits present but a few minor problems in low compression engines, whereas with engines'of higher compression ratios two more serious problems are berequire fuels of high octane number for most efficient coming increasingly prevalent, those of detonation and deposit-induced autoignition or wild ping. Although detonation can successfully be obviated by the utilization of organo-lead anti-knock agents such as tetraethyllead, it has been found that the severity of the wild ping problem often increases with the octane quality of the fuel. Hence, the automotive industry is faced with the dilemma resulting from the fact that each time the octane quality of the fuel is raised to coincide with increases in compression ratio, deposit-induced autoignition generally becomes more severe.

Ordinary detonation in the internal combustion engine has been defined as the spontaneous combustion of an appreciable portion of the charge, which results in an extremely rapid local pressure rise and produces a sharp metallic knock. The control of ordinary detonation may be effected by retarding ignition timing, by operating under part throttle conditions, by reducing the compression ratio of the engine, and by using fuels having high anti-knock qualities, that is, by using an organolead-containing fuel. Deposit-induced autoignition may be defined as the crratic ignition of the combustible charge by combustion chamber deposits resulting in uncontrolled combustion and isolated bursts of audible and inaudible manifestations of combustion, somewhat similar to knocking. Aside from the nuisance experienced by the passenger car operator, deposit-induced autoignition or wild ping often produces deleterious effects inasmuch as it is a precurser of preignition. Therefore, wild ping results in rough engine operating conditions and very often increases the Wear of engine parts, piston burning and the like. In contrast to ordinary detonation, deposit-induced autoignition or wild ping cannot be satisfactorily controlled by retarding ignition timing nor by operating under part throttle conditions. Inasmuch as automotive engineers are desirous of utilizing in internal combustion engines the highest compression ratios permitted by the commercially available fuels, the reduction of compression ratios to eliminate this problem is not desirable nor feasible. Indeed, it is the consensus of opinion among the designers of internal combustion engines that engine developments have heretofore been greatly hindered by the limitations imposed by deposit-induced autoignition. It is evident, therefore, that the present requirement for fuel having high antiknock qualities shall be greatly surpassed by future requirements. Notwithstanding attempts to attain these qualities by alternative means, it isentirely probable that the most satisfactorv method for the attainment of high octane fuels shall continue to be the use of anti-knock agents, particularly of the organolead type. As a result, there is a paramount need existing for a new and improved method for altering the physical and chemical characteristics of deposits and for modifying the combustion process such that the detrimental effects of deposit-induced autoignition may be markedly suppressed or be eliminated.

I have now found that a particular class of compounds effectively controls (by inhibiting and/ or preventing and/ or modifying) the deposit-forming tendencies of substantially hydrocarbon fuels, for example gasoline, jet fuels and the like, with resulting advantages. The hydrocarbon fuels of this invention are characterized by low depositforming tendencies with the result that an engine operated therewith shows exceptionally clean intake system combustion space, valves, ring belt area, cleaner spark plugs, etc.- The low deposit level in the engine, spark plugs, etc., minimizes surface ignition in all its manifestations, for example preignition, knock, wild ping, spark plug fouling, etc. The low deposit level reduces the engines octane requirement increase and deposits on surfaces contacted by the lubricating oil, such as piston skirts and cylinder walls, are very markedly reduced.

In addition, these compounds have an anti-catalytic effect, or, in other words, have the effect of suppressing or inhibiting the catalytic properties of the deposits found, especially the troublesome lead-containing deposits. Furthermore, these compounds are also effective corrosion inhibitors.

The class of compounds effective in this invention comprise esters ofalkenyl succinic acids and anhydrides thereof and such variations on these esters which include partial esters (i.e. esteracids) partial ester salts, monomeric esters, polymeric esters, and the like. Substantially any of the above esters can be employed, provided they are sufficiently soluble in the fuel to be effective as a deposit modifier.

The esters of alkenyl succinic acids employed in accordance with this invention are reaction products of alkenyl succinic acid or the anhydride thereof or their equivalent with any hydroxy organic material that is capable of reacting to form an ester, provided the prodnet is sufliciently soluble in the hydrocarbon fuel.

The alcohols employed in preparing the esters of this invention can vary widely. They can be monofunctional, difunctional, or higher functional, i.e. R(OI-I) wherein R is the radical to which the OH groups are attached. .Although R is generally hydrocarbon it may contain other elements and functional groups provided that these groups do not interfere with the use of the resulting ester. Thus, R may contain ether groups, ester groups, keto groups, aldehyde groups, thio groups, and the like. The small x in the above formula is a whole number of at least one, for example one-four or higher, but preferably one or two.

The simplest alcohol that can be employed is a monofunctional alcohol having the formula ROH wherein R is a hydrocarbon group for example, alkyl, cycloalkyl, aryl, alkaryl, aralkyl, a heterocyclic group, and the like. In addition, R may contain unsaturated groups, for example alkenyl, alkinyl, cycloalkenyl, etc. groups for example allyl alcohol, methallyl alcohol, oleyl alcohol, linoleyl alcohol, propargyl alcohol, etc.

Thus, alkyl monohydric alcohols are typefied by the following: methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadceanol, hexadecanol, octadecanol, and the like.

In addition, isomers, analogues, homologues, etc. of the above alcohols can be employed, for example iso' propanol, isob-utanol, sec-butyl alcohol and the like.

Aromatic alcohols can be also employed. These include aromatic compounds containing the OH group bonded directly to the ring, as in the case of a phenolic aim compound, as well as an aromatic substituted aliphatic compound for example benzyl alcohol, phenylethanol, phenoxyethanol, and the like. The aromatic group may also be substituted, for example, with halogens and the li e.

Cycloaliphatic alcohols may also be employed, for example cyclohexanol, cyclopentanol, terpineol, fenchyl alcohol, etc.

Another class of monohydric alcohols that can be employed are ether-alcohols. They are formed, for example, by reacting aliphatic alcohols with alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, octylene oxide, styrene oxide and other ot-fi epoxides. In addition the aliphatic alcohols can be reacted with mixtures of the above oxides as well as from block polymers by reacting first with one oxide, for example, ethylene oxide and then with another oxide for example propylene or butylene oxide. These ether-alcohols may be expressed by the formula R(OA) OH, wherein R is the radical derived from the alcohol, A is the radical derived from the alkylene oxide and x is the number of units of alkylene oxide added for example at least one, for example 1-100, but preferably 1 to 20. See Surface Active Agents and Detergents, Schwartz et a1., Inter science Publishers, pp. 163-166 (.1958).

Typical of the lower unit ether-alcohols, including sulfur analogues of these ether compounds, are those shown in the following:

Many of the above listed ether alcohols formed by the reaction of ethylene or propylene oxide with aliphatie alcohols are known in the art as Dowanols, Carbitols, or Cellosolves.

A group of alcohols especially adapted for use in the present invention are the so-called 0x0 alcohols, prepared by the reaction of carbon monoxide and hydro- 6d gen upon the olefins obtainable from petroleum products. Materials such as diisobutylene and C olefins are suitable for this purpose, also higher weight olefinic materials are sometimes employed. The alcohols obtained in this manner normally have a branched chain structure. The Oxo" process for the preparation of alcchols was developed in. Germany and. first described in this country in Roelen U.S. Patent No. 2,327,066, granted August 17, 1943.

In addition to monofunctional alcohols, polyfunctional 6 alcohols may be employed. Of the poly'functional, alcohol, the preferred embodiment is a glycol.

The glycols employed in preparing the esters of the present invention include ethylene glycol and any of the paraflinic homologues of the same containing, for example, up to 20 carbon atoms. These homologues may include, for example, propylene glycol, butylene glycols, pinacone, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, and the like. Since the glycols may also contain oxygen or sulfur atoms, compounds such as diethylene glycol, triethylene glycol, the polyethylene glycols of the formula HO (CH CH O) CH CH OH Where n is 1 to 26, and the polypropylene glycols of the general formula R R HO(H HO n( JH'( 3HOH where R or R is a methyl group and the other is hydrogen, and where n is 1 to 20, may likewise be employed. Glycols containing sulfur atoms in thioether linkages may also be employed, and these include such compounds as thiodiglycol and l,2 -bis(2-hydroxyethylmercapto) ethane. There also may be used glycols containing both oxygen and sulfur in similar linkages; such a compound is bis-[2-(2-hydroxyethoxy)ethyl] sulfide. For additional glycols, see the above Schwartz, Perry reference, for example, the block polymer glycols, etc.

In addition, aromatic diol may also be employed, for example -(OH) wherein is an aromatic group such as phenyl, X where X is a radical linking two phenyl groups such as Higher functional alcohols can also be employed for example glycerol, pentaerythritol, dipentaerythritol, manitol, etc.

Any alkenyl succinic acid anhydride or the correspond ing acid it utilizable in the present invention.

The general structural formulae of these compounds are:

wherein R is an alkenyl radical. The alkenyl radical can be straight-chain or branched-chain; and it can be saturated at the point of unsaturation by the addition of a substance which adds to olefinic double bonds, such as hydrogen, sulfur, bromine, chlorine, or iodine. It is obvious, of course, that there must be at least two carbon atoms in the alkenyl "radical, but there is no real upper limit to the number of carbon atoms therein. However, itis preferred to use an alkenyl succinic acid anhydride reactant having between about 8 and about 18 carbon atoms per alkenyl radical. Accordingly, when the term alkenyl succinic acid anhydride, isused herein, it must be clearly understood that it embraces the alkenyl succinic acids as well as their anhydrides, and the derivatives thereof in which the olefinic double bond'has been saturated as set forth hereinbefore. Thus, it includes the hydrogenated alkenyl group, i.e. alkyl succinic acids and anhydrides.

Non-limiting examples of the alkenyl succinic acid anhydride are thenyl succinic acid anhydrides;

ethenyl succinic acid; ethyl succinic acid anhydride; propenyl succinic acid anhydride; sulfurized propenyl suc- =cinic acid anhydride; butenyl succinic acid; 2-methyl- :butenyl succinic acid anhydride; 1,2-dichloropentyl suc- -cinic acid anhydride; hexenyl succinic acid anhydride; :hexyl succinic acid; sulfurized 3-methylpentenyl succinic acid anhydride; 2,3-dimethyl-butenyl succinic acid anhydnide; 3,3-dimethylbutenyl succinic acid; 1,2-dibromo-2- ethylbutyl succinic acid; heptenyl succinic acid anhydride;

-1,2-diiodooctyl succinic acid; octenyl succinic acid anacid anhydride; dodecenyl succinic acid anhydride; do-

decenyl succinic acid; 2-propylnoneny1 succinic acid anhydride; 3-butylocteny1 succinic acid anhydride; tridecenyl succinic acid anhydride; tetradecenyl succinic acid anhydride; hexadecenyl succinic acid anhydride; sulfurized octadecenyl succinic acid; octadecyl succinic acid anhydride; 1e2-dibromo-Z-methyl-pentadecenyl succinic acid anhydride; 8-propylpentadecyl succinic acid anhydride; eicosenyl succinic acid anhydride; l,2-dichloro-2-methylnonadecenyl succinic acid anhydride; 2-octyldodecenyl succinic acid; l,2-diiodotetracosenyl succinic acid anhydride; hexacosenyl succinic acid; hexacosenyl succinic acid anhydride; and hentriacontenyl succinic acid anhydride, as well as the corresponding acids and anhydrides of the above compounds.

The methods of preparing the alkenyl succinic acid anhydrides are well known to those familiar with the art. The most feasible method is by the reaction of an olefin with the maleic acid anhydride. Since relatively pure olefins are difiicult to obtain, and when thus obtainable, are often too expensive for commercial use, alkenyl succinic acid anhydrides are usually prepared as mixtures by reacting mixtures of olefins with maleic acid anhydride. Such mixtures, as well as relatively pure anhydrides, are utilizable herein. However, by making a careful fractionation of the olefin hydrocarbon, it is possible to control the number of carbons on the alkenyl group.

The reactions which occur to yield the esters employed in the practice of the present invention may be illustrated generally as follows:

Reaction I portrays the formation of monoand diesters of an alkenyl succinic anhydride. The preparation of the monoester is generally accomplished very easily by heating an alkenyl succinic anhydride and a molar equivalent of the desired alcohol at a temperature of approximately 150 C. for not more than three hours. It should be noted that in the preparation of esters from alcohols .boiling below 150 C. the reaction vessel should be provided with a return condenser to prevent the loss of any unreacted alcohol. The formation of the di-ester is somewhat more difficult as it is necessary to force the reaction either by means of a catalyst or in the presence of an azeotropic solvent which facilitates the removal of the water formed from the esterification. The preferred procedure is to heat the mono-ester and a molar equivalent of the desired alcohol in the presence of an azeotropic solvent until a molar equivalent of water has been driven from the reaction mass. The reaction vessel should be equipped with a trap and a reflux condenser to permit the return of the azeotrope to the reaction mass. The preparation of the di-ester may be carried out in one reaction rather than proceeding stepwise. Under such circumstances, it is advisable to heat the anhydride, alcohol and solvent at a moderate temperature such as 150 degrees C. for a short period of time in order to open the anhydride linkage. Then the temperature may be elevated to form the di-ester. In those instances where it is desired to prepare a di-ester in which the radicals are de rived from dissimilar organic hydroxy bodies, it is essential that the operations be carried stepwise. For example, the monoester should first be prepared from the lower boiling alcohol and the second esterification carried out with the higher boiling alcohol.

It will be seen from Reaction II that the monoester still retains an acidic carboxyl group which may be neutralized with a basic material to yield a mono-ester of alkenyl succinic acid. After the preparation of the mono-ester as described above, the ester-acid may be neutralized with any basic material to yield an ester-salt of alkenyl succinic acid. This reaction can be accomplished by following a simple titration in order to avoid any excess of the basic salt-forming reagent. Almost without exception, the salt formation may be carried out to substantial completion at atmospheric temperature by agitating the reactants. If there is cause to believe that the reaction has not procceded to completion, elevated temperatures may be used to assure completion of the reaction. At no time was it found necessary to raise the temperature in excess of 150 C. Obviously, the rate of the reaction is considerably increased by applying extreme heat. Most of these reactions are exothermic and the resulting temperature is usually effective in insuring a substantial yield of the desired ester-salt of alkenyl succinic acid.

Salt-forming reactants which are useful in the practice of our invention include the basic compounds of ammonia, alkyl amines (e.g., ethylamine, butylamine, laurylamine, octadecylamine), cycloalkyl amines (e.g., cyclohexylamine), aromatic amines (e.g., aniline, toluidine, anisidine and phenetidine), aralkyl amines (e.g., benzylamine), alkylolamines (e.g., monoethanolamine, diethanolamine, triethanolamine, and higher homologues), polyalkylene polyamines (e.g., diethylene triarnine, tetraethylene pentamine), and basic heterocyclic compounds having one or more than one basic nitrogen in the ring in which the hydrocarbon radical may be saturated or unsaturated and may have substituents of a non-polar character. Specific preferred examples of basic materials which are satisfactory for the purpose of this invention include butylamine, cycloehxylamine, toluidine, benzylamine, pyridine and the like. However, the metals which form cations generally leave a residue and are not generally employed, such as alkali metals, alkali earths, etc.

The products formed in the case of the polyfunctional alcohols can vary widely as will be illustrated by the following reactions in which a glycol is employed as illustrate In addition, it is possible to react alkenyl succinic anhydride with both monofunctional and difunctional alcohols.

For example, according to the following equation- The above equations are exemplary of some of the possible reactions that can occur when alkenyl succinic wherein B is a cation.

In general, deposit-preventing, inhibiting, and/ or modifying amounts of the compounds are employed. For example, the products of this invention are effective as a deposit-control additive in concentrations between 0.001 and 2'0 weight precent of the fuel. Generally, dirtier fuels having a higher concentration of olefinic components require higher concentrations whereas cleaner burning premium fuels are improved with respect to depositforming characteristics by smalled concentrations. In general, dirtier gasolines require a concentration between 0.01 and 1.0 percent whereas clean-burning premiumfuels only need a concentration of between 0.001 and 0.5 percent. There is no critical upper limit from a functional viewpoint but economics dictate that the concentration be less than one percent.

The compounds in this invention are efiective in conacid is reacted with difunctional alcohols or with mono trolling deposits in hydrocarbon fuels having boiling points up to about 500 F. or higher, although benefits also result when they are added to fuels containing residual stocks of higher boiling point. The major application of the additive is in gasoline for automotive engines wherein fuel-derived engine deposits have become a particularly vexing problem. The deposit-forming properties of fuels designed for use in jets are also improved by the compounds of this invention. They find particular application in jet fuels which are used as cooling mediums prior to their consumption. The compound-containing jet fuel is an excellent heat exchange medium since it is relatively free from deposits in the cooling system and burner nozzle where deposits cannot be tolerated.

The deposit-forming properties of both regular and premium gasolines and aviation gasolines, whether leaded and of the non-leaded type, are improved by the addition of these compounds. The gasolines to which they are added can be broadly defined as hydrocarbon fuels having a boiling point up to approximately 450 F.

Representative compounds for the above classes are incorporated for example in fuels used in automobile, aircraft, and jet engines. Laboratory tests are carried out employing these fuels in such systems.

The following examples are presented as illustrative of preparing the products employed in the present invention. In essence the monoester is prepared by heating the alcohol with the alkenyl succinic anhydride at 130-150" C. for about two-three hours. In the case of a low boiling alcohol, the completion of the reaction is indicated when this alcohol no longer refluxes. The formation of the diester is effected by heating the monoester with about one mole of alcohol or the anhydride with two moles of alcohol in the presence of an azeotroping agent and heating above 150 C. until the stoichiometric amount of water is recovered.

EXAMPLE I EXAMPLE H To one mole of steam distilled pine oil having specification of alpha-terpineol content, there is added one mole of an alkenyl succinic anhydride whose hydrocarbon chain contains on the average 11 carbon atoms. The mixture is heated at 150 degrees C. for three hours, and at this point, parts of S0 extract is added to yield the solution of the pine oil ester of alkenyl succinic anhydride.

EXAMPLE HI To one mole of alkenyl succinic anhydride having an approximate C hydrocarbon chain there is added one mole of allyl alcohol. The temperature of the mass is elevated to degrees C. and maintained at that point for three hours. In the initial stages of the reaction there is some evidence of allyl alcohol refluxing but as the reaction proceeded to completion the refluxing gradually .ceases. One hundred parts of S0 extract is added with stirring to yield the solution of the allyl ester of alkenyl succinic anhydride.

EXAMPLE IV To two moles of steam distilled pine oil having a specification of 85% alpha-terpineol content, there is added one mole of alkenyl succinic anhydride with a C to C range alkenyl group. The temperature is elevated to effect -1-l the loss of an aqueous-like distillate. The theoretical quantity of water is secured from the reaction mass over a period of six hours, with distillation beginning at 195 degrees C. and a maximum temperature of 206 degrees C. To the di-terpineol ester there is added 200 parts of a suitable hydrocarbon fraction such as S extract for purpose of placing the ester in solution to facilitate handling.

EXAMPLE V To two moles of undecyl alcohol there is added one mole of alkenyl succinic anhydride having an alkenyl group of the C to C range. The temperature is gradually raised to efiect the loss of an aqueous-like distillate. Water begins to form at about 200 degrees C. and after six hours at a maximum temperature of 215 degrees C. a

theoretical amount of water is removed. 200 parts of a suitable hydrocarbon fraction such as S0 extract is added to the reaction mass as a solvent yielding the di ester ina form easy to handle.

EXAMPLE VI In a two-liter three-necked flask provided with a stirrer and return condenser, connected to the flask by means of a water trap, there is placed one mole of alkenyl succinic anhydride having an alkenyl group of the C to C range and one mole of isopropanol. The mixture is heated with stirring for three hours at 150 degrees C. Any isopropanol which is condensed in the moisture trap is returned periodically to the reaction mass. The failure of any further quantities of isopropanol to be condensed and collected in the moisture trap is an indication of the completion of the reaction forming the mono-ester. To this mono-ester is added one mole of steam distilled pine oil having a specification of 85% alpha-terpineol content and 50 parts of a hydrocarbon fraction which is suitable for azeotropic distillation. The temperature is then elevated until the theoretical amount of an aqueous distillate has been secured in the moisture trap. This distillate is collected over a period of four hours and at a maximum temperature of 180 degrees C. The resulting product is the mixed di-ester of alkenyl succinic anhydride.

In view of the above description and the fact that the preparation of other compositions employed in this invention are prepared in the same manner, it would be unnecessary and repetitious to repeat the details of each pre- 1 Average.

- The products of the above examples which cont-ain 'ls free acid group can be neutralized with ammonia or amine to form ester-salts. Examples of materials which can be used to neutralize these materials comprise ammonia, butylamine, cyclohexyl amine, diethy-lenetriamine, etc. In fact, any of the amines described in my application Serial No. 790,351, filed of even date and assigned to the same assignee as the present invention can be employed.

TEST I Performance tests show that the present invention produces substantial improvement in engine cleanliness, as compared to the same fuel not containing the additive. The test procedure involves a 40 hour engine run on a dynamometer under conditions chosen to correlate, on" an accelerated scale, with field performance. In this test'a 216.5 cubic-inch, six-cylinder Chevrolet engine is run continuously for forty hours at a speed of 1900 r.p. m. (plus or minus 25 rpm.) under an engine load of 36 B.H.P. (plus or minus 1 B.H.P.). The jacket coolant inlet te1nperature is kept at 155 F. minimum, the jacket coolant outlet temperature is kept within two degrees of 170 F., and the crankcase oil temperature is kept within two degrees of 190 F. The air-fuel ratio is 14.5 (plus or minus 0.5) to 1. The spark advance is 35 (plus or minus 3). The spark plug gap, ignition cam angle, valve clearance, exhaust back pressure and other similar conditions are also maintained at predetermined values. Before the test, the engine is disassembled and cleaned, and a new set of piston rings is installed. The engine is given a standard two-hour break-in before the actual test is begun.

After the test runof 40 hours, the engine is dismantled and inspected, and is rated on ten items, as follows:

Piston skirt varnish rating. Cylinder wall varnish rating.

(3) Intake valve stem deposit rating. (4) Intake valve tulip deposit rating. (5) Intake port deposit rating.

(6) Overall engine sludge rating.

(7) Overall engine varnish rating.

On these first seven items, the rating runs between 0 for dirty to 10 for clean.

for each A perfectly clean engine will thus rate 100. A total rating of is considered acceptable if the piston skirt varnish is 7.5 or better.

The gasoline employed in the tests is composed of about 50% mixed thermal naphtha having about -400 F. boiling range, about 20% light straight-run naphtha having 95 -250 F. boiling range, about 25% heavy cracked (catalytic) naphtha having 270400 F. boiling range, and about 5% of light natural gasoline. It contains as additives about 1.75 ml. per gallon of tetraethyllead and an amine inhibitor in normal amounts. It analyzes 0.11% sulfur. Gum is present at about 2 to 5 mg. per ml. in the ASTM test and the copper dish test shows about 16-26 mg. of gum per 100 ml. The gasoline has the following volatility specifications: 10% evaporated at 134-150 F., 50% at 244-250 F., and 90% at about 360 F. The approximate composition of the gasoline is':

Percent Paratnns and naphthalenes, about 66 Olefins, about l6 Aromatics, about 18 Sulfur, about 0.1 Phenols, about 0.4

Nitrogem about, 0.001

The esters shown in the above table when tested in concentrations of 0001- weight percent gave cleaner eng'ines and therefore higher ratings than the control containing no additive.

An example of a high quality premium grade fuel with which similar results are obtained comprises mainly fluid catalytically cracked stock and straight run gasoline. This fuel has a 95 A.S.T.M. Research octane rating, contains 2.74 mi. of TEL fluid per gallon, had an API gravity of 60 to 65 and a boiling point range between 100 and 400 F.; the base fuel is negative in the copper corrosion test and has an oxidation stability in the ASTM test of 240 minutes minimum. This fuel also contains minor amounts of conventional gasoline-inhibitors, namely, approximately 6 pounds of N,N'-disecondary butyl-p-phenylenediamine, a gum inhibitor, per thousand barrels of gasoline, about 1.2 pounds of N,N'-disalicylidene-1,2-diaminopropane, a metal deactivator, per thousand barrels of gasoline, and about 1.1 pounds of lecithin, a tetraethyl lead stabilizer, per thousand barrels of gasoline.

Similar results are obtained with a high quality regular grade gasoline comprising a mixture of thermal cracked stock, fluid catalytically cracked stock and straight run gasoline. This regular base fuel has an 87.0 ASTM Research octane rating, contained 2.90 ml. of TEL per gallon, has an API gravity of 58.0 and a boiling range between 100 F. and 450 F.; the base fuel is negative in the copper corrosion test and has an oxidation stability in the ASTM test of 530 minutes minimum. The reference fuel also contains minor amounts of gasoline inhibitors, namely N,N-'disecondary butyl-p-phenylenediamine, lecithin, and N,N'-disalicylidene-1,2-diaminopropane;

These compositions are also similarly eifective when tested in an aviation grade gasoline as exemplified by a 115/130 grade aviation gasoline containing 4.6 ml. of tetraethyl lead.

The motor fuels employed in this invention comprise a mixture of hydrocarbons boiling in the gasoline boiling range. For instance, the gasoline employed can be a straight-run gasoline or a gasoline obtained from a conventional cracking process, or mixtures thereof. The gasoline can also include components obtained from processes other than cracking such as alkylation, isomerization, hydrogenation, polymerization, hydrodesulfurization, hydroforming, platforming or combinations thereof, as well as synthetic gasoline obtained from the Fischer- Tropsch and related processes.

TEST II Spark plug fouling A production model 1956 Oldsmobile Super 88 engine isusedto accomplish the evaluation. The engine is connected directly to a power absorption dynamometer through a conventional multiple disc coupling. The dynamometer and engine are fully instrumented to control operating conditions and to indicate data which are recorded hourly throughout the test.

Preparation of the engine for the test includes a thorough. cleaning, inspection and measurement of all components. The engine is assembled according to the manufacturers specifications. After subjecting the engine to an eight hour break-in a thirty-two hour oil consumption check follows. During this check a speed of 2000 r.p.m. and 50 B.H.P. is maintained. At eight hour intervals the oil is drained and weighed. Having established oil consumption stability the cylinder compression 'pressures are measured to indicate valve condition. The cylinder heads are removed and all combustion chamber deposits eliminated.

The cylinder heads are assembled to the engine and pre selected test spark plugs are installed for the first time. The engine starts on test schedule with an electro-mechanical intermittent controller attached to the throttle and dynamometer control which timed and actuated the throttle opening and dynamometer resistance for engine speed and load change. These changes are 2000 rpm. at 37.5 B.H.P. for five minutes and 450 rpm. at idle for one minute. Fifty of these cycles or iive hours comprise one interval. At the completion of each interval a check is made for misfiring at 2400 rpm. at full load. If no misfiring is observed the test continued for another interval of five hours. In the event of misfiring it is determined whether one or more spark plugs are failing. A criterion for test termination is three fouled plugs in three different cylinders. If less than three plugs fouled simultaneously the fouled plug or plugs are replaced with a new plug and the test continued until a total of three plugs fouled in three different cylinders. The reasons for replacing the fouled plugs with new plugs before continuing the test are:

A. To prevent upsetting test conditions which would effect fouling in other cylinders.

B. To assure that misfiring is caused by the plug or plugs in question.

C. To confirm that some abnormal condition in the cylinder is not causing unusually early fouling.

The foregoing procedure and conditions are observed for the first 139 hours of each test phase. At the end of 139 hours the conditions conducive to spark plug fouling are further enhanced. Consideration is carefully given to future possibility of test duplication before making any change. Beginning with the 140th hour of each test phase and continuing until phase termination the following changes are in effect:

(1) The air fuel ratio is decreased from 12.4:1 to 11.1: 1.

(2) The speed and load cycling is discontinued and changed to -a constant speed of 2200 r.p-.m. at 41.2 B.H.P.

(3) As a consequence of the above changes the fuel fiow Throughout the entire test a careful check is kept on oil consumption. At each 20 hours, as the test progresses, the engine is shut down for a crankcase oil level check. At each 60 hours the oil is changed.

The fuel treated with the additive is blended as follows:

A 4000 gallon capacity storage tank is flushed with the base fuel. 1200 gallons of base fuel are pumped into the tank. A circulatingpump is placed in operation with the intake at one end of the tank and the delivery at the opposite end of the required amount of additive is mixed with five gallons of the base gasoline. This mixture is slowly fed into the delivery stream of the fuel from the circulating pump. The fuel blend is recirculated for sixteen hours before start of the test.

7 The spark plugs selected for the test are AC-43. This spark plug is one degree colder in the heat range than the engine manufacturer reconnnends for this model. Twenty-four plugs are inspected and pre-tested under air pressure for firing for each test phase. From each batch of 24 plugs eight are selected which are nearly uniform in resistance at maximum pressure. All electrode gaps are adjusted to .040".

Specifications V nglne:

Oldsmobile 1956 Super 88 Type-No.

of cylinders 90 degree V-8. Valve arrangement In head, Bore and stroke 3% x 3 1 Piston displacement (cu. in.) 324.31. Compression ratio 9.25 :1. Max. brake horsepower, at 4400 r.p.m. 240.

Carburetor Rochester 4-barrel Front Rear Barrel Barrel A/F Jet J 'et Ratio sizes sizes Standard Equipment 49 61 13.121 -139 hours of test 55 51 12. 4:1 140 hours to termination of test 59 55 11. 1:1

Equipment air cleaner used. The air-fuel ratio was determined by a Cambridge Exhaust Gas Tester.

Exhaust back pressures and intake manifold vacuum are measured by means of mercury manometers. Barometric pressure is observed on a conventional mercury barometer and was corrected for temperature. Engine 011 pressure is measured by a standard Bourdon-type gage.

The rate of fuel consumption is determined on a weight basis using a tip balance. A flowmeter in the supply line provides a check upon engine fuel consumption determined by weighing.

Engine speed is determined by an electronic counter.

Spark plug performance characteristics are observed by means of a multiple trace oscilloscope.

Both incipient fouling and 100% fouling of each spark plug is recorded in hours.

The base fuel used for the test operations is described as follows:

Composition-mixture of straight run and catalytically cracked gasolines:

Gravity, API 58.8 Bromine number 53 Doctor Negative Fuels containing the compositions of this invention in weight percent of 0.001 to according to this test are superior to corresponding fuels containing no additive.

Since spark plug fouling is a function of the lead content of the gasoline, the optimum amount will vary with such content. Although weight ratios of 0.001-2% or more can be employed in gasolines containing about 3 cc.

of tetraethylene lead or its equivalent/gallon or gasoline, generally 0.001'-'1% is usually sufiicient for anti-fouling purposes. However, it should be understood that the optimum amount on the weight basis for one par- 5 ticular compound may not be the optimum amount for.

another compound. One reason for this is that the effectiveness of the compounds varies from one compound to another. Another reason is the variance of molecular weights so that one compound may be twice the molecular weight of another on weight basis. However, by proper adjustment of concentrations, anti-fouling can be effected. The principles also apply to the other ratios herein stated.

TEST III These compounds in the above table are also tested in a 100 hour full scale reciprocity engine test employing Military Specification MIL-G5572A grade 115/145 fuel in a Wright R3350-30W compound engine operated according to the following cycle:

Time per cycle (min) Idle 10 Take-off power and speed 5 Normal rated power and speed 30 Cruise 10% normal rated power and 93% normal rated -30 Cruise 90 Total 255 Two types of spark plugs are used in the engine: The AC-285, a platinum fine wire electrode plug and the AC-265 and 275 massive electrode plugs at the end of the test, the engine is disassembled and inspected for deposits and deleterious efiects.

Fuels containing the compositions of this invention in weight ratios of 0.001 to 5% by weight according to this test are superior to corresponding fuels containing no additive.

TEST IV The compounds in the above tables are also tested in a hour full scale gas turbine engine test in a Pratt & Whitney I57P29 gas turbine engine employing Specification MIL-J-5624D grade IP-4 fuel. The engine is operated for 100 hours and cycled in accordance with the Specification MILE-5009 Model qualification test. After 100 hours of operation the engine combustion components and turbine sections are disassembled and inspected for deposits and deleterious effects.

Fuels containing the compositions of this invention in weight ratios of 0.001 to 0.5% by weight according to this test are superior to corresponding fuels containing no additive.

Although the present invention has been described with preferred embodiments, it is to be understood that modifications may be resorted to without departing from the spirit and scope thereof.

The invention includes various fuels such as all grades of gasolines which may contain a wide variety of additives such as anti-oxidants, organolead stabilizers, organic dyes, solubilizers, etc., as well as the halide scavengers generally employed such as ethylene dibromide and/or ethylene dichloride and other scavengers for example those disclosed in the patents listed above relating to such compositions. Such variations and modifications are considered to be within the purview and scope of the appended claims.

Having thus described my invention, what I claim as new and desire to obtain by Letters Patent is:

1. A process of preventing, inhibiting and modifying the formation of deposits in internal combustion and jet engines employing a substantially hydrocarbon fuel which comprises burning in such engines a fuel consisting of a liquid hydrocarbon having a boiling point up to about 500 F. and a minor amount, in the range of approximately 0.001 to 2.0 weight percent of said fuel suflicient to prevent, inhibit and modify such deposits, of an ester of (1) a member selected from the group consisting of an alkenyl succinic acid and the anhydride thereof, having 3-31 carbon atoms on the alkenyl group and (2) an alcohol, said ester being soluble in said liquid hydrocarbon and being composed of only carbon, hydrogen and oxygen.

2. The process of claim 1 where the alkenyl radical has 818 carbon atoms and the alcohol has 1-2 hydroxy groups.

3. The process of claim 2 where the hydrocarbon fuel is gasoline.

References Cited in the file of this patent UNITED STATES PATENTS 2,386,445 De Groote et al. Oct. 9, 1945 2,450,221 Ashburn et al Sept. 28, 1948 2,568,746 Kirkpatrick et a1. Sept. 25, 1951 2,715,108 Francis Aug. 9, 1955 2,733,235 Cross et a1. Jan. 31, 1956 

1. A PROCESS OF PREVENTING, INHIBITING AND MODIFYING THE FORMATION OF DEPOSITS IN INTERNAL COMBUSTION AND JET ENGINES EMPLOYING A SUBSTANTIALLY HYDROCARBON FUEL WHICH COMPRISES BURNING IN SUCH ENGINES A FUEL CONSISTING OF A LIQUID HYDROCARBON HAVING A BOILING POINT UP TO ABOUT 500*F. AND A MINOR AMOUNT, IN THE RANGE OF APPROXIMATELY 0.001 TO 2.0 WEIGHT PERCENT OF SAID FUEL SUFFICIENT TO PREVENT, INHIBIT AND MODIFY SUCH DEPOSITS, OF AN ESTER OF (1) A MEMBER SELECTED FROM THE GROUP CONSISTING OF AN ALKENYL SUCCINIC ACID AND THE ANHYDRIDE THEREOF, HAVING 3-31 CARBON ATOMS ON THE ALKENYL GROUP AND (2) AN ALCOHOL, SAID ESTER BEING SOLUBLE IN SAID LIQUID HYDROCARBON AND BEING COMPOSED OF ONLY CARBON, HYDROGEN AND OXYGEN. 